The present invention relates to a mechanism which controls the braking action of a door or window casement, and in particular to a braking mechanism mounted between the frame and the casement of a window or a door and being of a type having a telescopic tube and a piston rod which is slideably supported in the telescopic tube.
A braking device of this type specifically designed for a skylight casement is disclosed in EP 0 723 058 A2. This braking device is of telescope type and includes a rectangular telescopic tube in which a rectangular flat push rod is slideably guided. The telescopic tube and the flat push rod have free ends which are connected to a coupling link for connection to the frame and the casement of a window.
Neighboring the end of the push rod that is retracted in the telescopic tube is a rectangular cutout for receiving a braking device. This braking device includes two braking jaws having conical surfaces that are facing each other for support upon a wedge lodged in the cutout.
Also mounted within the cutout is a spring in which a pin of the wedge projects and which acts upon the braking jaws, thereby effecting a force-locking connection of the braking jaws with the wedge, with the outer surfaces of the braking jaws being supported by the inner surfaces of the telescopic tube.
An inadvertent disengagement of the push rod and the braking device from the telescopic rod is prevented by forming on the inside of the telescopic tube beads or depressions which extend inwardly from the inner friction surfaces of the telescopic tube. In addition, the flat push rod is formed at a small distance from the rectangular cutout with beads which cooperate with the beads of the telescopic tube during extension stroke of the push rod for limitation of this extension stroke.
As the above described beads form sloping surfaces, it can happen that at great exertion of pressure upon the telescopic assembly, the telescopic tube gets damaged or deformed. This pressure can happen especially when the casement of a window is being pushed open hard so that the telescopic rod and the pushing rod get jammed into each other.
Through the impact stress upon the telescopic assembly in the end position thereof, there is a further danger that the casement itself or the attachment points to the frame and the casement are damaged.
With this known construction, an additional disadvantage is also that due to the normal surface tolerances, a smooth guiding of the braking jaws along the inner surface of the telescope tube and therefore a smooth and even braking action, remains unattainable. Furthermore, the known braking device can only be used on windows with casements that are rotatable around a single axis.